GCC builtins in LDC - compiler interoperability

[kinke]

On Wednesday, 15 July 2020 at 23:31:39 UTC, Cecil Ward wrote:
> Oh, shame. There’s no __builtin_unreachable in ldc? I wonder if 
> I could work around this with LDC then.

With D / LDC, there's almost always a workaround. In this case, 
using inline LLVM IR (as 'unreachable' is an IR instruction for 
LLVM):

-----
bool foo() nothrow;

void unreachable()
{
     import ldc.llvmasm;
     // due to a current LDC bug, a dummy parameter is required
     __ir!(`unreachable`, void, int)(0);
}

int bar()
{
     int r = 123;
     if (foo())
     {
         r = 456;
         unreachable();
     }
     return r;
}
-----

With -O, bar() is optimized to a `return 123`.